This application entitled "Development of a Brief Screener for Research in Autism Spectrum Disorders" addresses broad challenge area (04) Clinical Research, 04-MH-101* Autism: Addressing the challenge. The proposal aims to develop a research screening instrument based on questions from the Social Communication Questionnaire (SCQ: Rutter, Bailey, &Lord, 2003) and the Autism Diagnostic Interview- Revised (ADI-R;Rutter, LeCouteur &Lord, 2003) that can be more effectively and practically employed in research studies of autism spectrum disorders (ASD). The newly developed measure will be the ADI Research Screening Questionnaire, a brief parent-report instrument that is designed to identify ASD in children ages 2 to 18 years. Development and validation of the new measure will involve two very large groups of children from multiple sites across the U.S. Existing data from a total of 2293 assessments of children with ASD, 792 assessments of children with non-ASD diagnoses, and 600 typically developing siblings of children with ASD will form the basis of the Measure Development sample. A separate sample of 1340 participants with ASD, 510 participants with non-ASD diagnoses, and 200 typically developing siblings of children with ASD will be recruited from ongoing research studies and specialty diagnostic clinics to validate the newly developed measure. Analyses of data from these two independent samples will result in a new instrument that can be used to rapidly ascertain potential participants for ASD research. The availability of a measure that quickly and accurately differentiates children with ASD from children with other developmental disorders will be invaluable to etiological and epidemiological research efforts, as it will significantly reduce the time and expense that is currently required to designate study participants as either having or not having ASD. Development of a Brief Screener for Research in Autism Spectrum Disorders This project will result in the development of a new screening instrument that can be used for research studies of autism spectrum disorders (ASD). Because of the need to identify large numbers of participants for genetics studies and other investigations of the causes of ASD, researchers require a way to rapidly screen large numbers of children and identify those who are highly likely to have a diagnosis of ASD. This project will provide researchers with the ability to quickly select potential participants so that they can more effectively carry out their investigations into the causes of ASD.